1. Field of the Invention
Vehicle drive trains with a turbo-charged and mechanically charged (supercharged) internal combustion engine are well-known to the person skilled in the art and are also known as turbocharger-turbocompound systems. During turbocharging, a compressor which compresses the fresh air supplied to the internal combustion engine is driven by means of an exhaust gas turbine which is arranged in the exhaust gas stream of the internal combustion engine. The drive connection between the exhaust gas turbine and the compressor is usually a purely mechanical one, as also advantageously according to the present invention.
2. Description of the Related Art
In the case of a turbocompound, the drive power of the mentioned or an additional exhaust gas turbine in the exhaust gas stream of the internal combustion engine is added to the mechanical drive power of the internal combustion engine in that the exhaust gas turbine drives the crankshaft of the internal combustion engine at least indirectly. A hydrodynamic coupling is usually arranged for reducing the torsional oscillations in the drive connection between the exhaust gas turbine and the crankshaft.
Although the mentioned turbocharger-turbocompound systems can improve the efficiency of the drive train in many load ranges, the known systems come with the disadvantage that load ranges can also occur in which the overall system has a worse efficiency and/or more unfavorable emissions than comparable systems without turbocharger and without turbocompound.
The present invention is based on the object of providing a drive train and a method for controlling the power transmission in a drive train, especially a motor vehicle drive train, in which the mentioned disadvantages are avoided. In particular, a strategic control shall be created which optimizes the utilization of existing powers for improving the efficiency in the overall load profile.